14.10.1 Ecosystems and Material Cycles: Water, Carbon, and Sulfur

Question 1

Ecosystems and Material Cycles: Water, Carbon, and Sulfur

Answer 1

• All ecosystems need a flow of energy and a cycle of materials.
• In the carbon cycle, carbon dioxide (CO2) is converted to glucose by photosynthesis, and glucose is converted to CO2 by respiration.
• In the hydrologic cycle, the sun’s energy drives water evaporation. The water then condenses to form precipitation.
• In the sulfur cycle, volcanoes and factories emit sulfur oxides. These sulfur oxides are incorporated into vegetation, which decomposes, thereby completing the cycle

Question 2

ecosystem

Answer 2

• All ecosystems need two basic things:
  1. flow of energy
  2. cycle of materials
• Review: Energy flows through ecosystems in one direction and cannot be recycled.
• Materials like elements are recycled by ecosystems. The chart on the left shows six fundamental elements used by living organisms. The mnemonic to remember them is the nonsense word “SPONCH.” They are sulfur, phosphorous, oxygen, nitrogen, carbon, and hydrogen.

Question 3

carbon cycle

Answer 3

• In the carbon cycle, carbon dioxide (CO2) is converted to glucose by photosynthesis; glucose is converted to CO2 during respiration. The image on the left illustrates the cycling of CO2 in an ecosystem.
• A surplus of CO2 exists in the atmosphere because of industry and large-scale deforestation.

Question 4

hydrologic cycle

Answer 4

• In the hydrologic cycle, the sun’s energy drives water
  evaporation, which then condenses to form precipitation. Over the open ocean, more water evaporates than precipitates. Also, over large tracts of forested area, a large amount of water evaporates because of plant transpiration (the evaporation of water by plants through the leaves.) Over most land areas, more water precipitates than evaporates.

Question 5

sulfur cycle

Answer 5

• The sulfur cycle is fairly complex. On land, trees and other photosynthetic organisms absorb sulfur oxides and incorporate them into organic matter. Dead organic matter may be converted to sulfates by bacteria. The burning of fossil fuel releases large amounts of sulfur oxides into the atmosphere, resulting in acid rain. In the ocean, certain kinds of algae contain large concentrations of sulfur compounds. When the algae decompose, they release sulfur compounds that may be available for absorption by terrestrial plants.

Question 6

What two elements are being added to global cycles by human activity?

Answer 6

• carbon and sulfur

Question 7

Which of the following illustrates the carbon cycle in its simplest form?

Answer 7

• 6CO2 + 6H2O C6H12O6 + 6O2

Question 8

Which of the following is the main abiotic source of carbon in the environment for the carbon cycle?

Answer 8

• carbon dioxide in the air